Recipe: Breakfast Stromboli

Name: Recipe: Breakfast Stromboli
Ingredients: 1 teaspoon olive oil; 8 ounces uncooked breakfast sausage, casings removed; 1/4 medium yellow onion, finely chopped; 4 large eggs; 1 tablespoon whole or 2% milk; 1/4 teaspoon kosher salt; Freshly ground black pepper; 1 pound pizza dough, at room temperature for at least 1 hour; 1 cup shredded sharp cheddar cheese, divided; 1 tablespoon coarsely chopped fresh parsley leaves; 1 large egg; 1 teaspoon water